Abstract. Although the causative agent of bovine viral diarrhea was initially categorized as 1 species, phylogenetic analysis revealed that these viruses belong to 2 different species, Bovine viral diarrhea virus 1 (BVDV-1) and BVDV-2, with 2-11 subgenotypes within each species. Distribution of species and subgenotypes has been shown to vary with geographic region. Whether distribution shifts over time is not known. Surveys conducted between 1994 and 2008 reported 3 subgenotypes circulating among cattle in the United States: BVDV-1a, BVDV-1b, and BVDV-2a. The average percent prevalence of BVDV-1a, BVDV-1b, and BVDV-2a strains reported in surveys before 2001 were 21%, 43%, and 36%, respectively. Surveys conducted on viruses isolated after 2001 reported decreasing percentages of BVDV-1a and BVDV-2a strains, with BVDV-1b strains accounting for 75-100% of samples. Comparison of these surveys is confounded by differences in geographic location, collection methods, and sample type used in the survey. The purpose of the present study was to determine whether the prevalence of BVDV subgenotypes shifted in samples collected from the same geographic region and by the same laboratory over time. BVDV strains isolated in years 1988BVDV strains isolated in years , 1998BVDV strains isolated in years , and 2008, at the Texas Veterinary Medical Diagnostic Laboratory, Amarillo, Texas, were genotyped, and the prevalence of BVDV-1a, BVDV-1b, and BVDV-2a strains were determined. Typing, on the basis of phylogenetic analysis, was done on 148 samples. The strongest trend detected among these samples was a pronounced decrease in the number of BVDV-1a strains over time.

Results suggested that seroprevalence of paratuberculosis among purebred beef cattle in Texas may be greater than seroprevalence among beef cattle in the United States as a whole; however, this difference could be attributable to breed or regional differences in infection rates or interference by cross-reacting organisms. Veterinarians should be aware of risk factors for paratuberculosis as well as the possibility that unexpected serologic results may be found in some herds.

Bovine trichomoniasis is a sexually transmitted disease that results in infertility, abortion, and calf age variability. To date, management strategies include testing for Tritrichomonas foetus and culling of infected males. Challenges associated with testing include cost of culture medium, time and labor burden of sample incubation and processing, and adverse effects of bacterial growth on detection sensitivity. To overcome these challenges, we developed a direct reverse-transcription quantitative real-time PCR (direct RT-qPCR) utilizing smegma, eliminating the use of culture medium. In an analysis of 166 field samples (56 positives and 110 negatives as determined using microscopic reading of cultures as the reference test), the direct RT-qPCR exhibited 100% diagnostic sensitivity and 100% specificity, whereas the currently employed qPCR (culture qPCR), which utilizes cultured samples, exhibited 95% diagnostic sensitivity and 100% specificity. Agreement between direct RT-qPCR and culture qPCR was 98%. Moreover, direct RT-qPCR identified 3 more positive samples and exhibited lower quantification cycle (Cq) values among positives by culture reading than did culture qPCR (direct RT-qPCR Cq range = 14.6-32.3 vs. culture qPCR Cq range = 18.7-37.4). The direct RT-qPCR enables simplified sample collection, elimination of culture medium, faster results, applicability in cows, and lower cost than culture qPCR.

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